Pumping systems with fluid density and flow rate control

Abstract

A system includes a first plurality of pumps connected to draw from a clean fluid supply junction. A second plurality of pumps is operatively connected to a dirty fluid supply. A first valve is connected between the clean fluid supply junction and the dirty fluid supply for supplying clean fluid to the dirty fluid supply. A second valve is connected to feed a dirty fluid to the dirty fluid supply. A controller is operatively connected to the first and second valves and to the first and second pluralities of pumps for controlling downhole concentration and flow rate of proppant from the dirty fluid supply, wherein downhole concentration and flow rate are varied across a continuous spectrum.

What is claimed is: 
     
       1. A system, comprising:
 a first plurality of pumps connected to draw from a clean fluid supply junction; 
 a second plurality of pumps operatively connected to a dirty fluid supply; 
 a first valve connected between the clean fluid supply junction and the dirty fluid supply for supplying clean fluid to the dirty fluid supply; 
 a second valve connected to feed a dirty fluid to the dirty fluid supply; 
 a controller operatively connected to the first and second valves and to the first and second pluralities of pumps for controlling downhole concentration and flow rate of proppant from the dirty fluid supply, wherein the downhole concentration and flow rate of proppant are varied across a continuous spectrum; and 
 a plurality of sensors operatively connected to the controller for feedback to control the downhole concentration and flow rate of proppant during the pumping operation, wherein the plurality of sensors includes: 
 a first volume flow meter upstream of the clean fluid supply junction for measuring total flow of clean fluid into the first and second pluralities of pumps; 
 a second volume flow meter in a flow path fluidly connecting the clean fluid supply junction to the first plurality of pumps for measuring flow of clean fluid into the first plurality of pumps; 
 a third volume flow meter downstream of the second valve for measuring flow of the dirty fluid into the dirty fluid supply; and 
 a densometer in series with the dirty fluid supply upstream of the second plurality of pumps for measuring concentration of proppant. 
 
     
     
       2. The system as recited in  claim 1 , wherein the controller includes machine readable instructions configured to cause the controller to follow a programmed stimulation method that varies the downhole concentration and flow rate of proppant as a function of time. 
     
     
       3. The system as recited in  claim 1 , further comprising if one or more of the pumps in the first and second pluralities of pumps fails, automatically adjusting the remaining operational pumps in the first and second pluralities of pumps to maintain the desired flow rate of proppant and concentration of proppant without requiring user input. 
     
     
       4. The system as recited in  claim 1 , wherein each pump in the first plurality of pumps and each pump in the second plurality of pumps includes an electric motor. 
     
     
       5. The system as recited in  claim 4 , wherein at least one of: the electric motor is connected to produce linear motion in each of the respective pumps; and/or the electric motor is a linear motor. 
     
     
       6. The system as recited in  claim 5 , wherein the linear motor includes a rod that is connected to a respective pump piston slidingly engaged in piston chamber, wherein the pump piston divides the piston chamber into a first end and a second end, further comprising:
 a first one-way suction valve in fluid communication with the first end of the piston chamber, configured to admit a first fluid into the first end of the piston chamber therethrough; 
 a first one-way discharge valve in fluid communication with the first end of the piston chamber, configured to discharge the first fluid from the first end of the piston chamber therethrough; 
 a second one-way suction valve in fluid communication with the second end of the piston chamber, configured to admit a second fluid into the second end of the piston chamber therethrough; and 
 a second one-way discharge valve in fluid communication with the second end of the piston chamber, configured to discharge the second fluid from the second end of the piston chamber therethrough; 
 wherein the first fluid and the second fluid is in fluid communication with same fluid source; and 
 wherein the fluid source is the clean fluid supply or the dirty fluid supply. 
 
     
     
       7. The system as recited in  claim 1 , wherein the controller is connected to control each pump in the first plurality of pumps and each pump in the second plurality of pumps, and is operatively connected to receive feedback from the first, second, and third volume flow meters and the densometer for closed-loop control of the pumps. 
     
     
       8. The system as recited in  claim 7 , wherein the controller is configured to:
 compare a desired downhole flow concentration and flow rate of proppant mixed with a water mixture to actual downhole flow concentration and flow rate of proppant mixed with the water mixture based on the feedback from the first, second, and third volume flow meters and the densometer; and 
 adjust individual flow rates of the first and second pluralities of pumps and/or adjust the first and second valves to make the actual downhole flow concentration and flow rate of proppant with the water mixture match the desired downhole flow concentration and flow rate of proppant with the water mixture. 
 
     
     
       9. The system as recited in  claim 8 , wherein the adjusting to match the actual downhole flow concentration and flow rate of proppant with the water mixture with the desired downhole flow concentration and flow rate of proppant with the water mixture includes matching the desired downhole flow concentration and flow rate of proppant mixed with the water mixture that changes as governed by a programmed stimulation method that varies downhole proppant flow rate and/or concentration as a function of time. 
     
     
       10. The system as recited in  claim 7 , wherein each pump in the first plurality of pumps and each pump in the second plurality of pumps includes an electric motor. 
     
     
       11. The system as recited in  claim 10 , wherein at least one of:
 the electric motor is connected to produce linear motion in each of the respective pumps; and/or 
 the electric motor is a linear motor. 
 
     
     
       12. A method, comprising:
 controlling downhole concentration and flow rate of proppant, wherein the downhole concentration and flow rate of proppant are varied across a continuous spectrum, wherein the controlling downhole concentration and flow rate of proppant includes: receiving sensor feedback into a controller from a plurality of sensors; controlling a first plurality of pumps operatively connected to a clean fluid supply junction, a second plurality of pumps operatively connected to a dirty fluid supply, a first valve connected between the clean fluid supply junction and the dirty fluid supply and a second valve connected to feed a dirty fluid to the dirty fluid supply to match an actual downhole flow rate and concentration of proppant with a desired flow rate and concentration of proppant, and wherein the receiving sensor feedback includes receiving sensor feedback from: 
 a first volume flow meter upstream of the clean fluid supply junction for measuring total flow of clean fluid into the first and second pluralities of pumps; 
 a second volume flow meter in a flow path fluidly connecting the clean fluid supply junction to the first plurality of pumps for measuring flow of clean fluid into the first plurality of pumps; 
 a third volume flow meter downstream of the second valve for measuring flow of the dirty fluid into the dirty fluid supply; and 
 a densometer in series with the dirty fluid supply upstream of the second plurality of pumps for measuring concentration of proppant, wherein the method further comprising determining the actual downhole concentration and flow rate of proppant based on measurements from the first, second, and third volume flow meters and the densometer. 
 
     
     
       13. The method as recited in  claim 12 , wherein the step of controlling to match the actual downhole flow rate and concentration of proppant with the desired flow rate and concentration of proppant includes matching the desired flow rate and concentration of proppant that changes as governed by a programmed stimulation method that varies downhole proppant flow rate and/or concentration as a function of time. 
     
     
       14. The method as recited in  claim 12 , further comprising receiving user input for updated desired flow rate and concentration of proppant, wherein the step of controlling to match the actual downhole flow rate and concentration of proppant with the desired flow rate and concentration of proppant includes matching the desired flow rate and concentration of proppant that changes as governed by updated desired flow rate and concentration of proppant. 
     
     
       15. The method as recited in  claim 12 , further comprising:
 balancing flow among operational pumps in the first plurality of pumps with one another; and 
 balancing flow among operational pumps in the second plurality of pumps with one another. 
 
     
     
       16. The method as recited in  claim 12 , further comprising if one or more of the pumps in the first and second pluralities of pumps fails, automatically adjusting remaining operational pumps in the first and second pluralities of pumps to maintain the desired flow rate and concentration of proppant without requiring user input. 
     
     
       17. The method as recited in  claim 16 , wherein the step of automatically adjusting remaining operational pumps in the first and second pluralities of pumps includes at least one of adjusting pump speed and/or adjusting a pump valve or choke. 
     
     
       18. The method as recited in  claim 12 , wherein each pump in the first plurality of pumps and each pump in the second plurality of pumps includes an electric motor, wherein the step of controlling to matching the actual downhole flow rate and concentration of proppant with the desired flow rate and concentration of proppant includes the controller varying electrical power to at least one of the respective motors. 
     
     
       19. The method as recited in  claim 18 , wherein each pump in the first plurality of pumps and each pump in the second plurality of pumps is a double acting pump and wherein the respective electric motor, being a linear motor, is connected to produce linear motion in each of the respective pumps, wherein controlling each pump in the first plurality of pumps operatively connected to the clean fluid supply junction and each pump in the second plurality of pumps operatively connected to the dirty fluid supply includes pumping fluid from each pump in the first plurality of pumps and each pump in the second plurality of pumps in both linear directions of the respective linear motor. 
     
     
       20. The method as recited in  claim 19 , wherein the step of pumping fluid from each pump in the first plurality of pumps and each pump in the second plurality of pumps in both linear directions of the respective linear motor includes actuating the respective linear motor at a first rate in a first stroke direction and actuating the respective linear motor at a different rate in a second stroke direction reverse of the first stroke direction.